founder
"Founder" is a word with a few distinct and interesting meanings. Most people know it as a noun — the person who starts something — but it also works as a verb with a completely different meaning. Here are the most important senses.
In the context of horses, to founder means the animal stumbles badly or becomes lame — unable to walk properly due to injury or illness. This is a more specialized use, but you may encounter it in literature or historical texts.
equestrian, veterinary, historical · Still used, more common in older or specialized texts